In conventional additive or three-dimensional fabrication techniques, construction of a three-dimensional object is performed in a step-wise or layer-by-layer manner. In particular, layer formation is performed through solidification of photo curable resin under the action of visible or UV light irradiation. Two techniques are known: one in which new layers are formed at the top surface of the growing object; the other in which new layers are formed at the bottom surface of the growing object. An early example is Hull, U.S. Pat. No. 5,236,637. Other approaches are shown in U.S. Pat. Nos. 7,438,846, 7,892,474; M. Joyce, US Patent App. 2013/0292862; Y. Chen et al., US Patent App. 2013/0295212 (both Nov. 7, 2013); Y. Pan et al., J. Manufacturing Sci. and Eng. 134, 051011-1 (October 2012), and numerous other references. Materials for use in such apparatus are generally limited, and there is a need for new resins which will provide diverse material properties for different product families if three-dimensional fabrication is to achieve its full potential.
Southwell et al., US Patent Application Publication No. 2012/0251841, describe liquid radiation curable resins for additive fabrication, but these comprise a cationic photoinitiator (and hence are limited in the materials which may be used) and are suggested only for layer-by-layer fabrication.
Velankar, Pazos, and Cooper, Journal of Applied Polymer Science 162, 1361 (1996), describe UV-curable urethane acrylates formed by a deblocking chemistry, but they are not suggested for additive manufacturing, and no suggestion is made on how those materials may be adapted to additive manufacturing.